In order to conserve water it is common practice to install water saving shower heads. The devices currently used for this are quite rudimentary in operation. They typically reduce consumption by employing a small inlet to the shower head to reduce flow. The volume of water emanating from the head may also be decreased, simply by using reduced diameter spray holes. While each of these designs are to some extent successful, their effectiveness is limited because a reduction in flow rate also reduces the pressure of the spray. Consequently shower heads which operate at the current benchmark of 9 litres per minute for an AAA rating have problems with low spray pressure, restricted spray patterns and clogging of the outlet holes in the spray head. Also, for many people a shower spray of 9 litres per minute from existing devices feels inadequate.
One way of economising on flow rate whilst maintaining a desirable spraying effect is to have the primary flow of water entering the shower head chamber tangentially through an inlet in its peripheral side wall that is constrained to follow a circular flow path, and exits at an outlet in an end wall at or near the central axis of the chamber. This primary flow of water that follows a circular path forms a vortex commencing internally at or near the peripheral side wall and increases in velocity and pressure towards the outlet. If a further inlet is provided at substantially 90 degrees to the circular flow path and a secondary control flow of water is fed through this further inlet it regulates and atomizes the primary flow into a spray that emanates from the outlet.
This method of atomising and forming a spray is not limited to water applications and is employed in uses involving other fluids. One such application is in a fuel injection valve where atomisation of the fuel is desirable. U.S. Pat. No. 6,161,782 (Heinbuck et al.) depicts a fuel atomising disk in FIG. 2, in which a secondary control flow is provided at substantially 90 degrees to the primary circular flow path, and regulates and atomises the primary flow into a spray.
A disadvantage of providing a secondary control flow at substantially 90 degrees to the primary circular flow (or vortex) path, is that it tends to interfere and break down the vortex.